2-(n-butyl)-3-[[2′-(tetrazol-5-yl)biphenyl-4-yl]methyl]-1,3-diazaspiro[4.4]non-1-en-4-one (Irbesartan) is represented by Formula I.

Irbesartan is a powerful angiotensin II receptor antagonist (blocker). Angiotensin is an important participant in the renin-angiotensin-aldosterone system (RAAS) and has a strong influence on blood pressure.
Many processes are disclosed in the art for the preparation of Irbesartan. Irbesartan has been generally prepared as per the process disclosed in EP-A-0 454 511, i.e. by reaction of 2-(n-butyl)-3-[[2′-(cyano)biphenyl-4-yl]methyl]-1,3-diazaspiro[4.4]non-1-en-4-one either with tributyltin azide and triphenyl chloromethane in xylene at reflux, by elimination of the triphenylmethyl protecting group and by isolation from a solution in ethyl acetate, duly dried. The other commonly used process is disclosed in C. A. Bernhart et al., J. Med. Chem., 1993, 36, 3371-3380. The process involves reaction of 2-(n-butyl)-3-[[2′-(cyano)biphenyl-4-yl]methyl]-1,3-diazaspiro[4.4]non-1-en-4-one directly with tributyltin azide, in xylene at reflux and isolation from a solution in dichloromethane, duly dried. The compound thus prepared, [Formula (I)], is presented in the form of stable, non-hygroscopic needles, which can be stored and formulated without any degradation.
U.S. Pat. Nos. 5,196,444 and 5,399,578 and describe similar procedures for the synthesis of some non-peptide angiotensin II inhibitors wherein the use of trimethyltin azide is reported in presence of toluene as a solvent for the conversion of aromatic nitrles into tetrazoles. All these processes require trialkyltin azide as a reagent, which is not safe to handle and is costly. The reaction time is usually long, ranging from 36 hours to 4 days. The isolation of product from such reaction mixtures can be tedious, requiring several critical layer separations, and the yield obtained is generally low.
U.S. Pat. No. 5,629,331 describes a process for the preparation of Irbesartan Form A and B wherein the aromatic nitrile is treated with sodium azide in presence of triethylamine hydrochloride in 1-methylpyrrolidin-2-one as solvent at a temperature of 121-123° C. The solvent used is costly and not easily recovered, making the process unsuitable for commercial scale production.
U.S. Pat. No. 6,162,922 has described a process for the preparation of Irbesartan which involves treating the Spiro intermediate of Formula III with halomethyl cyanobiphenyl intermediate of Formula IV in presence of a water and water immiscible solvent, a base and a phase transfer catalyst.
The processes known in the prior art for preparing Irbesartan involve tedious workup procedures, e.g., a large number of steps, which include the protection and subsequent deprotection, and isolation of intermediates, as well as separations by column chromatography. The processes of the art involve tedious workup to isolate the required product and this results in excessive production times, which in turn renders the process more costly and less eco-friendly; thus the processes are not suitable for commercial scale up. Accordingly, there remains a need for a simple, commercially advantageous process.